A STUDY  OF  THE  EFFECT  OF  TEMPERATURE  CONTROL  ON  THE 
YIELD  OF  THE  PRODUCTS  OF  DESTRUCTIVE  DISTILLATION 

OF  CERTAIN  HARD  WOODS 


By 


THARRAWADDY  MAUNG  MAUNG 


THESIS 

FOR  THE 

DEGREE  OF  BACHELOR  OF  SCIENCE 

IN 

CHEMICAL  ENGINEERING 


COLLEGE  OF  LIBERAL  ARTS  AND  SCIENCES 
UNIVERSITY  OF  ILLINOIS 


1921 


Digitized  by  the  Internet  Archive 
in  2016 


https://archive.org/details/studyofeffectoftOOmaun 


UNIVERSITY  OF  ILLINOIS 


THIS  IS  TO  CERTIFY  THAT  THE  THESIS  PREPARED  UNDER  MY  SUPERVISION  BY 

rawaddy  _ l-laiing.  Jfeimg. 

ENTlTLED-L-SJiud.y-ja£— tii6-JS££ent-ja£-IILainpej2a±nr.B— O-ontr-QiL-QiL-iLhe. 

Y_ie  Id  _ _of_  _t  he  _ Pr_o  due  ts  _ _o  f _ JD  es  t_r  u_ct_i  y_e  _ D i_s_t  i_l  la  t_i  o 11  _ of  _ _C_  e rt  a in  JJar  d 
Woods 

IS  APPROVED  BY  ME  AS  FULFILLING  THIS  PART  OF  THE  REQUIREMENTS  FOR  THE 
degree  OF  .BaGhfi X.Qr_ _Q f_ _ S_q. ionne _ _in  _ Ch gmi c_a  1_ _En,g i_ne_e ring. 


Instructor  in  Charge 


Approved  : TJt_. 


HEAD  OF  DEPARTMENT  OF 


■ 


' 


Ac  kn o w 1 e dgme nt 


The  author  desires  to  express  his 
thanks  to  Professor  W.S.Putnum  under  whose 
direction  this  research  was  carried  out, 
in  sincere  appreciation  of  excellent  ad- 
vice, kindly  encouragement  and  many  fa- 
vours throughout  the  course  of  the  work, 
and  also  to  Dr.  T.E.Iayng  for  many  val- 
uable suggestions  and  help. 


Table  of  Contents 


pages 

I.  Introduction  and  purpose  of  Investigation 1 

II.  Factors  and  Conditions 2 

III.  Method  of  Distillation  and  Collection 3 

(1)  Installation  of  Electric  Furnace 6 

(2)  Device  for  Controlling  Temperature 7 

IV.  Moisture  Determination 8 

V.  Analysis  of  Products 10 

VI.  Results 11 

VII.  Conclusions 12 

VIII.  Discussion 13 

IX.  Bibliography 14 


1 


A Study  of  the  Effect  of  Temperature  Control  on  the 
Yield  of  the  Products  of  Destructive  Distillation 
of  Certain  Hard  Woods 

I 

Introduction  and  Purpose  of  Investigation. 

In  recent  years  there  has  "been  a boom  in  India-rubber  planta- 
tions in  Burma,  from  where  the  author  comes.  A great  number  of  new 
plantations  have  sprung  up  and  they  are  increasing  in  number  yearly. 
Older  plantations  having  come  to  maturity,  there  is  a great  demand 
for  acetic  acid,  which  is  used  for  curing  rubber.  Up  to  this  time 
the  acid  has  been  imported  from  other  countries  and  not  a single 
concern  manufactures  it  within  the  country.  Burma  has  immense 
tracts  of  forest  in  which  many  hard  wood  trees  are  to  be  found  in 
abundance,  of  which  th6  most  important  are  Dahat  (Tectona  Hamilton- 
ia),  Thitni  (Wendlandia  Sp.),  Te  (Diospyros  Burmanica),  Thamon 
(Boscia  Variabilis),  Hman  (Gardenia  Sp.),  Than  (Terminalia  Oliver!), 
In  (Diptero  Carpus),  and  Pyinkado  (Zylia  dolabri  formis).  These 
could  be  utilised  in  the  manufacture  of  acetic  acid.  There  are  many 
advantages  in  favour  of  manufacturing  the  acid  within  Burma.  First- 
ly, there  is  an  abundance  of  cheap  wood.  Secondly,  the  labour  is 
comparatively  very  cheap.  And  thirdly,  there  is  a great  demand  for 
the  acid  in  the  country  itself.  Having  talked  this  over  with  Pro- 
fessor D.F. McFarland , I find  that  he  feels  that  a study  of  the  com- 
parative yield  of  the  products  of  American  woods  with  those  of  Bur- 
mese would  be  very  timely  and  interesting.  He  also  suggests  a study 
of  the  effect  of  temperature  control.  The  author  took  up  this  sub- 
ject in  accordance  with  his  suggestions.  But  unfortunately  Burmese 


2 


woods,  shipped  from  Burma,  were  lost  on  the  way,  and  owing  to  many 
difficulties  encountered  in  building  the  electric  furnace,  there 
was  time  only  for  the  investigation  of  the  effect  of  temperature 
control  on  the  yields  of  the  products  of  distillation  of  Oak  and 
Bir  ch. 

II 

Factors  and  Conditions. 

The  factors  and  conditions  that  effect  the  yield  in  the  pro- 
ducts of  destructive  distillation  of  wood  are  the  following: 

(1) .  The  size  and  shape  of  retort. 

(2) .  The  different  parts  of  the  tree  used  in  dist illation- -lumber , 

slab  wood,  heart-wood  and  bark. 

(3) .  The  period  of  aging. 

(4) .  The  size  and  form  of  wood. 

(5) .  The  moisture  content. 

(6) .  The  rate  of  heating. 

(1). 

Variations  due  to  (1)  are  removed  by  distilling  in  the 
same  retort. 

Variations  due  to  conditions  2-4  are  removed  by  sav/ing  off 
small  pieces,  about  1"  x 1”  x 16"  from  one  large  piece  of  lum- 
ber for  a series  of  runs. 

Yields  are  calculated  on  the  dry  weight  of  the  wood  to 
take  care  of  the  difference  in  moisture  content,  (5),  as  runs 
are  made  on  different  days. 

The  rate  of  heating  is  the  only  condition  that  is  varied. 
Therefore  the  effect  on  the  yield  of  the  products  will  be  that 
due  to  the  temperature  control. 


% 


, ' $ ■ 


* 


. 


3 


III 

Method  of  Distillation  and  Collection. 

Small  pieces  of  wood  sawed  off  approximately  1"  x 1"  x 16” 

W6re  placed  in  an  electrical  furnace.  Just  before  the  furnace  was 
charged,  a small  sample  of  wood  was  taken  out  for  moisture  determi- 
nation, and  the  rest  were  weighed.  For  a series  of  runs  the  furnace 
was  heated  up  as  fast  as  it  could  be  heated.  The  distillate  was  con- 
densed and  collected.  The  uncondensed  gases,  which  had  a very  strcng 
choking  smell  were  burnt  after  passing  through  two  water  condensers— 
one  of  iron  receiving  the  gases  first,  and  the  other  of  glass  re- 
ceiving the  cooler  gases.  Ho  attempt  was  made  to  analyse  the  gases. 
The  distillate  was  allowed  to  settle  for  about  24  hours,  and  the 
charcoal  was  allowed  to  cool  for  the  same  period  of  time.  The  wa- 
ter y distillate,  pyroligneous  acid,  was  separated  from  the  tary  dis- 
tillate by  decantation. 

For  the  other  series  of  runs,  the  furnace  was  charged  in  the 
same  way,  with  nearly  the  same  amount  of  wood;  a sample  being  saved 
as  before  for  the  determination  of  moisture.  In  this  series,  the 
furnace  was  heated  slowly  over  night  till  it  reached  the  temperature 
of  220  C-230  C,  when  it  was  heated  up  rapidly  to  about  320  C.  The 
current  was  then  switched  off.  But  owing  to  the  exothermic  nature 
of  the  reactions,  the  temperature  continued  to  rise  till  it  reached 
about  440  G.  The  distillates  W6re  condensed,  collected,  and  separa- 
ted as  before.  In  both  cases  "tar  coke"  was  separated  from  charcoal 
and  weighed  by  itself,  this  weight  being  added  to  the  total  tar  in- 
stead of  to  the  weight  of  charcoal.  "Tar  Coke"  is  the  name  given 
the  material  oocuring  in  the  retort,  which  was  clearly  a residue 

from  the  distillation  of  tar,  by  Hawley  and  Palmer.*  Temperature 

* 


U. S.  Dept.  Agriculture  Bulletin  ITo.  129 


4 

was  recorded  as  follows : Through  the  cap  of  the  retort  a small  iron 

pipe  was  screwed  in,  which  reached  into  the  middle  of  the  retort. 
Into  this  was  inserted  a Chrome 1-Alumel  thermo-couple.  With  the  aid 
of  a volt-meter,  calibrated  to  read  the  temperature  in  degrees  cen- 
tigrade, the  temperatures  were  read  off  directly.  Two  typical  data 
sheets  follow: 

Table  I. 

Sample  data  sheet -short  run. 

Run  Ho.  V.  May  11,  '21 

Kind  of  wood- -Oak 

Actual  weight  of  charge— 5888  gm. 

Dry  weight  of  charge — 5582.93  gm. 

Time  Temperature  Ho.  of  Resistance  Remarks 

coils  in  till  the 
time  of  reading. 

May  11 

3:35  P.M.  50 
4:35  " 120 

4:55  " 165 

5:01  " 180 

5:10  " 200 

5:25  " 240 

5:30  " 260 

5:50  " 315 

6:05  " 330 

6:23  " 350 

6:30  " 368 

6:35  " 365 

7:30  ” 273 


Current  switch  on  full. 


1 - no  sliding  resistance 

1 _ IT  I! 

1 — ” ” 

1 — ” ” 

1 - " " 

P _ Tl  IT 

7 - all 


Gas  evolution  begins 


Gas  evolution  violent 
All  resistance  put 
in. 

Switch  off. 


Max.  Temperature. 


5 

Tar  collected  = 550-52  gm. 

Wt.  of  charcoal  = 1170  gm. 

Total  P-acid  - 1375cc. 

Dissolved  tar  in  lOOcc  P-acid  = 14.7760  gm. 

Distilled  acid  from  lOOcc  P-acid  = 124cc. 

Av.  cc.  of  IT.  HaOH  required  to  neutralise  lOcc  distilled  acid-18. 04cc 
Steam  distilled  acid  from  100  g.  tar=  1115cc. 

Av.  cc.  n.  ITaOH  required  for  50cc  acid  (from  tar)  I 5.1cc. 

Pinal  alcoholic  distillate^  254.  6 gm. 

Sp.  gr.  at  25  = .9806  (corrected  for  balance). 

Table  II. 

Sample  data  sheet -long  run. 

Run  ITo.  IV.  Hay  9,  1921 

Kind  of  Wood- -Oak 

Actual  v/eight  of  Charge — 3963.2  gm. 

Dry  Weight  of  Charge — 3676.77  gm. 


Time  Temp,  in  degrees  c.  Ho.  of  Resistance  Remarks 

coils  in  till  the 
time  of  reading. 


May ' 21 


10.50  P.M.  7-all  sliding  resis- 


May  1 21 

tance 

9:00  A.M. 
9:3 

220 

7 

- 

Tl 

II 

3 resist  coils 
taken  out 

9 :30  " 

260 

4 

— 

II 

It 

3 more  taken 
Out. 

10:00  " 

365 

1 

- 

II 

Tf 

violent  evo- 
lution ofgas 

10:11  " 

390 

1 

— 

It 

ii 

3 coils  put 
in 

10:15  " 

400 

4 

II 

Tl 

current  sv;itcl: 
off 

Time 


6 


Temp. 


10:30 

A.M. 

430 

10:35 

it 

458 

10:40 

it 

440 

10:45 

tt 

436 

1:30 

P.M. 

286 

Tar  collected  “ 382.4  gm. 
Weight  of  chare oalz  1089  gm. 


IIo.  of  Resistance  Remarks. 

coils  in  till  the 

time  of  reading. 


maxiunram  temp. 


Dissolved  tar  in  lOOcc  P-acid  = 14.0459  gm. 

Distilled  acid  from  lOOcc  P-acid  - 137  gm. 

Av.  cc  n.  FaOH  required  to  neurtralise  10  cc  acid  Z 15.8 
Steam  distilled  acid  from  100  gm.  tar-  1068cc. 

Av.  cc  n.  PaOH  required  to  neutralize  25cc  acid  (tar)  z 3.5 
Pinal  Alcoholic  distillate  r 267-89  gm. 

Sp.  gr.  of  alcohol  at  28.5  C corrected  for  error  in  balances. 983738. 
Ilf  (i)  Installation  of  Electric  Furnace 
An  old  electric  furnace  was  obtained.  It  was  made  out  of  a 6 
inch  pipe,  42  inches  long,  screwed  in  at  one  6nd,  a four  way  con- 
nection, whose  top  and  furthest  end  openings  were  plugged;  while 
the  other  end  a flange  to  carry  a heavy  cap  was  screv/ed  in.  To  the 
middle  of  the  cap  was  screwed  in  a -jr  inch  iron  pipe  closed  at  the 
other  end.  The  pipe  extends,  when  the  cap  is  fitted  on,  to  the 
center  of  the  pipe.  This  serves  as  a thermometer-well.  As  the  old 
wire  was  burnt  out,  it  was  unwound  and  the  pipe  cleaned. 

About  1/8  inch  layer  of  alundum  cement  was  applied  around  the 


main  part  of  the  pipe  and  allowed  to  dry  for  24  hours. 


Then  150 


7 


ft.  of  Kichrome  wire  II o . 16  was  wound  spirally  over  it.  Over  the 
wire  was  again  applied  another  layer  of  alundum  cercent  about  3/16 
inch  in  thickness.  Water  was  used  to  mix  the  cement.  Y/hen  dry, 
the  pipe  was  supported  on  a frame  made  out  of  ■£  inch  pipes.  The 
coil  was  then  cut  into  thre6  equal  sections,  which  were  connected 
to  the  three  outside  sliding  rheostats.  Th6  pipe  was  then  enclosed 
in  a sheet-metal  cylinder,*  20.6  inches  in  diameter  and  41  inches 
long.  The  space  in  between  was  filled  loosely  with  sil-o-cel 
which  consists  mainly  of  silica. 

jll  ( zl)  Device  for  Controlling  Temperature. 

The  temperature  was  controlled  by  sliding  and  box  rheostats 
outside  the  furnace.  Th6  box  rheostat  consisted  of  7 pairs  of  high- 
resistant  wires,  with  an  arrangement  to  put  in  any  number  of  coils 
up  to  7,  as  shown  in  the  following  diagram.*  This  was  connected 
to  the  main  switch.  Three  sliding  rheostats  were  connected  in  par- 
allel to  a lead  from  the  box.  The  main  adjustment  was  made  by 
means  of  the  box,  while  the  finer  adjustments  for  each  coil,  are 
made  with  the  respective  sliding  rheostats.  The  temperature  could 
be  controlled  only  so  long  as  the  reaction  was  not  fully  started. 
When  fully  started,  the  exothermic  nature  of  reaction,  rendered  the 
control  arrangements  useless.  The  following  table  shows  the  adjust- 
ments rheostats  and  the  resulting  voltages  and  amperes. 


* See  diagram  p.  7 , and  photograph  p.  7 


10 


V 

Analysis  of  Products. 

Different  methods  of  analysis  give  different  results,  so  it 
is  necessary  to  adopt  an  uniform  method  in  all  determinations , in 
order  that  the  results  may  he  comparable.  The  method  adopted  in 

1 ohxo 

these  series  of  experiments  is  according  to  Klar,  as  used  by  Haw- 

2 

ley  and  Palmer,  chemists  in  Forests  Products  Laboratory. 

Pyroligneous  Acid. 

fh6  pyroligneous  acid  was  analyzed  by  the  methods  described 
by  Klar  for  the  determination  of  acetic  acid,  wood  alcohol,  and 
dissolved  tar.  For  the  acetic-acid  and  dissolved  tar  determina- 
tions, lOOcc  of  pyroligneous  acid  were  distilled  at  a maximum  tem- 
perature of  140°C,  until  practically  no  further  distillate  appeared, 
when  lOOcc  of  water  were  added  and  distilled  off  as  before.  The 
residue  in  the  flask  was  weighed  and  computed  as  dissolved  tar, 
while  for  the  acetic  acid  determination  a convenient  part  of  the 
distillate  was  titrated  with  normal  sodium  hydroxide  solution,  with 
phenolphtalein  as  indicator. 

The  wood  alcohol  was  determined  by  distilling  60  per  cent  from 
a 1- liter  sample  of  the  pyroligneous  acid  and  adding  an  excess  of 
sodium  hydroxide  to  the  distillate,  again  distilling  60  per  cent, 
and  after  again  adding  sodium  hydroxide,  making  a third  distilla- 
tion of  60  per  cent.  The  final  distillate  was  accurately  weighed 
and  the  specific  gravity  determined  by  means  of  a Westphal  balance 

at  room  temperature  and  corrected  to  15.56  G by  using  the  alcohol- 
1 

metric  Table  in  the  Pharmacopoeia  of  the  United  States  of  America. 

1.  Technolo^ie  der  Holzverkohlung  p.  337. 

2.  U.S.  Dept,  of  Agriculture.  Bulletin  no.  129 


Tar 


11 

The  amount  of  aoetic  acid  in  the  settled  tar  was  determined, 

O O 

after  Klar,  by  distilling  100  grams  of  the  tar  at  150  to  140  “until 
the  watery  distillate  caased,  then  passing  steam  through  the  resi- 
due until  no  more  acid  was  found  in  the  distillate,  the  latter  be- 
ing then  titrated,  as  in  the  pyroligneous-acid  analysis,  and  added 
to  that  found  in  the  pyroligneous  acid. 

Charcoal. 

When  it  was  sufficiently  cooled, — at  least  24  hours  after  the 
run — the  charcoal  was  removed  from  the  retort.  It  was  separated 
from  the  "tar  coke"'  and  weighed.  The  percentage  was  computed  on 
the  basis  of  dry  wood.  "Tar  coke"  was  weighed  by  itself  and  added 
to  the  total  tar. 

YI.  . 

Results . 

The  yields  of  total  acetic  acid  (100$),  total  tar, and  wood  al- 
cohol (100  $) , expressed  in  percentages  of  the  oven-dry  weight  of 
the  material  distilled,  are  shown  in  Table  IV. 


Table  IY. 

No. 

and 

of  runs 
kind 

Dry  wt . of 
wood  gm. 

dT 

/° 

acid* 

cja  alcohol 

fo  tar  : 

$char- 

coal 

Oak. 

I. 

Short 

4029.8 

4.94 

.4.98 

14.62 

31.8 

II. 

Long 

3570 

7.96 

1.07 

11.14 

31.5 

III. 

Tf 

3620 

6.53 

.668 

9.53 

34.7 

IY. 

ti 

3676- 77 

7.47 

1.14 

17.5 

29.7 

V. 

Short 

3582.93 

5.4 

.505 

15.4 

32.7 

VI. 

u 

3716.35 

5.95 

.715 

16.7 

35.1 

- 


. 


. 

' 


• , 


' 


, 

■ 

■ 


12 


No.  of  runs 
and  kind 

Dry  wt.  of 
wood  gm. 

cjo  acid* 

% alcohol 

tar 

$ 

charcoal 

Average  for 

long  runs 

7.32 

.959 

12.72 

31.96 

Average  for 

short  runs 

5.43 

.572 

15.57 

33.2 

Birch 

Till.  Short 

4519.5 

6.87 

1.24 

7.66 

35. 

VII.  Long 

3550.58 

7.53 

1.28 

9.02 

57. 

* Acid 

in  tar,  which 

was  added 

to  the  main 

acid , 

determina- 

tion,  was  computed  from  only  the  collected  tar,  without  the  dis- 
solved tar  and  the  "tar  coke". 

There  are  a few  inconsistencies  in  the  results  of  different 
runs,  due  perhaps  to  some  errors  in  the  analysis  of  the  products. 
Percentage  of  alcohol  in  short  run  no.  YI  is  greater  than  that  of 
the  long  run  no.  III.  Percentage  of  tar  in  long  run  no.  IV  is 
greater  than  that  of  any  of  the  short  runs.  Again  the  percentage 
of  charcoal  in  long  run  III  is  greater  than  those  of  the  short  runs 
nos.  I and  V. 

In  spite  of  these  inconsistencies , the  averages  agree  with  the 
general  tendencies  of  the  results. 

As  the  building  of  the  electric  furnace  and  getting  it  into 
running  order,  took  a greater  part  of  the  time,  determinations  of 
other  hard  woods  were  impossible  within  the  time  allowed  for  com- 
pletion of  the  thesis. 

VII 

Conclusions. 

Prom  the  study  of  table  III  the  following  conclusions  may  be 
drawn:  In  the  distillation  of  oak,  by  heating  very  gradually  at 

the  start,  very  appreciable  increase  in  the  yields  of  acetic  acid 


13 


and  alcohol,  over  those  from  the  rapid  heating,  were  obtained, 
while  the  yields  of  tar  and  charcoal  are  less  than  those  of  the 
short  runs. 

In  the  distillation  of  Birch  the  yields  from  the  long  run  is 
greater  in  every  product  than  those  from  the  short  run.  As  there 
were  no  check  runs  on  these^two,  the  results  are  open  to  question. 

VIII 

Discussion. 

No  attempt  has  been  made  to  analyse  the  uncondensed  gases. 

They  were  burnt  at  the  end  of  the  outlet  from  the  second  condenser, 
and  computed  by  difference.  In  recent  developments  in  the  commer- 
cial destructive  distillation  of  hard  woods,  the  gases  are  conduc- 
ted back  into  the  retort  to  insure  a thorough  extraction  of  the 
products.  In  big  plants,  where  batteries  of  retorts  are  in  var- 
ious stages  of  operation,  the  gases  may  be  utilized  to  heat  other 
retorts.  As  for  heating  its  own  retort,  it  is  hardly  necessary, 
because  wh en  the  reaction  once  properly  started,  will  go  on  to  com- 
pletion owing  to  heat  given  out  by  the  exothemic  reaction.  The 
nature  of  this  reaction  has  been  taken  advantage  of  and  commercially 
developed  to  save  fuel  in  heating  the  retorts. 

The  effect  of  catalyzers  * on  the  yield  of  products  in  destruc- 
tive distillation  of  hard  woods,  has  hlso  been  studied,  but  has  not 
yet  become  commercially  important. 


* 


Jour,  of  Ind.and  Eng.  Ghem.  April  1918,  p.  264,  R.C. Palmer 


8 


Table  IV 


Amperes 


Resistance 

in 

Voltage 

Coil 

I 

II 

III 

7 coils 

217 

1.00 

1.00 

2.5 

6 " 

217 

3.00 

3.00 

2.75 

5 ,T 

216 

5.50 

3.25 

5.00 

4 " 

216 

3.75 

3.5 

3.25 

3 ” 

216 

4.00 

3.75 

3.50 

2 

215 

4.25 

4.00 

3.75 

1 

215 

4.50 

4.25 

4.00 

r-  " 

214 

6.00 

5.00 

5.25 

* Last 

line 

gives 

readings  with  all 

the  sliding  resistances 

out.  All  others 

were 

read  with  all  the 

sliding  rheostats 

in  full 

IV 

Moisture  Determinations. 

As  all 

the 

result 

s to  be  comparable 

must  be 

based  on 

the  dry 

wood,  it  was  necessary  that  the  moisture  content  of  the  woods  be 
carefully  determined.  Air  drying  will  not  drive  off  all  moisture 
as  pointed  out  by  C.iJ. Davison  in  his  thesis.  The  question  then 
arises  as  to,  at  what  temperature  and  how  long  the  wood  must  be 
heated  in  order  that  they  may  be  thoroughly  dried  without  decompo- 
sition. 

Up  to  the  time  of  C .11. Davidson' s experiments  on  the  calorific 
values  of  American  woods,  no  definite  information  could  be  obtained 
as  to  the  minimum  and  the  maximum  temperature  at  which  the  wood 
can  safely  be  dried.  In  1916,  working  under  Prof.  S.W.Parr,  he  has 
given  us  this  information,  which  has  proved  quite  valuable.  The 
following  are  the  conclusions  he  arrived  at. 

1.  "The  total  loss  in  weight  of  all  th6  woods  is  arrived  at  and  a 


substantially  constant  weight  secured  at  105  C in  either  air  or 
carbon  dioxide  and  practically  no  variation  occurs  on  prolonged 
drying  through  seven  hours,  the  limit  of  the  test." 

2.  Since  the  loss  in  weight  in  air  is  substantially  the  same  as  in 
carbon  dioxide  for  the  prolonged  periods  of  heating,  it  is  assumed 
that  there  is  no  oxidation  at  that  temperature. 

o 

3.  fhat  the  total  loss  and  a constant  weight  are  obtained  at  157 
in  air  or  GOg  and  that  practically  no  variations  occur  on  heating 
through  the  7th  hour. 

4.  xh6re  is  no  oxidation  at  137° G in  an  atmosphere  of  air.  This 
statement  is  based  upon  the  fact  and  the  changes  in  loss  of  weight 
are  substantially  the  same  in  both  carbon  dioxide  and  air. 

5.  fhere  is  a small  difference  between  the  loss  in  volatile  con- 

O £> 

stituents  at  137  G and  the  loss  at  105  G.  But  the  difference  does 
not  amount  to  more  than  0.3  percent  on  the  average  for  7 hours  of 
heating. " * 

On  the  basis  of  this  information,  the  author  f6els  safe  to  con- 
sider that  woods  are  thoroughly  dried  when  heated  at  115-120° C for 
two  hours. 

Methods . 

A thin  slip  of  the  material  was  sawed  off,  (just  before  the 
charge  was  weighed),  and  accurately  weighed.  It  was  then  heated  in 
a Freas  constant  temperature  electric  oven,  (whose  inside  dimensions 
are  12"  x 12"  x 14"),  at  115-120°  G for  two  hours.  It  was  then 
cooled  in  a dessicator  for  half  an  hour,  and  weighed  again.  The 
dry  weight  of  the  charge  was  computed  from  the  ratio  of  these  two 
weights. 

* Calorific  values  of  American  Woods,  1916. 


14 


Bibliography. 

1.  C.  II. Davidson. 

Calorific  Values  of  American  Y/ood. 

Thesis  for  Degree  of  M.S.  U.  of  111.  1916. 

2.  L.F. Hawley  and  R.C. Palmer, 

Yields  from  the  Destructive  Distillation  of  Certain  Hardwoods. 
U.S.Dept.  of  Agriculture  Bulletin.  ITo.  129. 

3.  M.  Klar . 

Technologie  der  Holzverkohlung,  1910. 

4.  Pharmacopoeia  of  the  U.3.A. 

5.  P.  Dumesny  and  J.  Hoyer . 

Wood  Products:  Distillates  and  Extracts,  1908 

6.  R.C. Palmer. 

The  Effect  of  Catalysers  on  the  yield  of  Products  in  the  De- 
structive Distillation  of  Hardwoods. 

Jour,  of  Ind.  and  Eng.  Chen.  April  1918,  p.  264. 

7.  R.C. Palmer  and  H.Cloukey. 

The  Influence  of  Moisture  on  the  yield  of  Products  in  the  De- 
structive Distillation  of  Hardwoods. 

Jour,  of  Ind.  and  Eng.  Chem.  April  1918,  p.  2o2. 


